Mixed Carbonates and Siliciclastics along the Coast of Southern Belize (Central America): Sediment Cores as Archives of Late Quaternary Coastal Development and Major Storms
The modern southern shelf of Belize is characterized by a carbonate-to-siliciclastic transition. Along the coast, quartz sand, that is brought into the system from the hinterland by rivers and small streams, may form small deltas and is transported along the coast by currents to form beaches, berms, and sand spits. Behind berms and sand spits, shallow coastal lagoons, mangrove swamps, marshes, and flood plains occur. Tidal deltas are found occasionally. Mangrove coastline without beaches or sand barriers is rare. Twenty-six cores with an average length of 2.8 m taken along five traverses across the coast were taken in order to detail late Pleistocene and Holocene coastal evolution and to identify event (storm) layers. Late Pleistocene facies as recovered in core are largely greenish to reddish loams with quartz grains. Holocene facies include brown to black (organic-rich) muds, peats, and quartz sand, as well as mollusk shell and coral coquinas. Lithologic repetitions in the cores suggest laterally shifting facies. Retrogradation and aggradation may have occurred during rapid to moderate sea-level rise such as during the early and mid Holocene. Slow sea-level rise or stalling sea level produced progradation as observed in the late Holocene. Coquinas are interpreted as either expressions of colonization events and/or storm deposits. Radiocarbon dating of peat, wood, mollusk shells, and coral skeletons is currently under way and will allow detailed facies correlations.
AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California